include/linux/eventpoll.h

   1 /*
   2  *  include/linux/eventpoll.h ( Efficient event polling implementation )
   3  *  Copyright (C) 2001,...,2006  Davide Libenzi
   4  *
   5  *  This program is free software; you can redistribute it and/or modify
   6  *  it under the terms of the GNU General Public License as published by
   7  *  the Free Software Foundation; either version 2 of the License, or
   8  *  (at your option) any later version.
   9  *
  10  *  Davide Libenzi <davidel@xmailserver.org>
  11  *
  12  */
  13
  14 #ifndef _LINUX_EVENTPOLL_H
  15 #define _LINUX_EVENTPOLL_H
  16
  17 /* For O_CLOEXEC */
  18 #include <linux/fcntl.h>
  19 #include <linux/types.h>
  20
  21 /* Flags for epoll_create1.  */
  22 #define EPOLL_CLOEXEC O_CLOEXEC
  23
  24 /* Valid opcodes to issue to sys_epoll_ctl() */
  25 #define EPOLL_CTL_ADD 1
  26 #define EPOLL_CTL_DEL 2
  27 #define EPOLL_CTL_MOD 3
  28
  29 /*
  30  * Request the handling of system wakeup events so as to prevent system suspends
  31  * from happening while those events are being processed.
  32  *
  33  * Assuming neither EPOLLET nor EPOLLONESHOT is set, system suspends will not be
  34  * re-allowed until epoll_wait is called again after consuming the wakeup
  35  * event(s).
  36  *
  37  * Requires CAP_BLOCK_SUSPEND
  38  */
  39 #define EPOLLWAKEUP (1 << 29)
  40
  41 /* Set the One Shot behaviour for the target file descriptor */
  42 #define EPOLLONESHOT (1 << 30)
  43
  44 /* Set the Edge Triggered behaviour for the target file descriptor */
  45 #define EPOLLET (1 << 31)
  46
  47 /*
  48  * On x86-64 make the 64bit structure have the same alignment as the
  49  * 32bit structure. This makes 32bit emulation easier.
  50  *
  51  * UML/x86_64 needs the same packing as x86_64
  52  */
  53 #ifdef __x86_64__
  54 #define EPOLL_PACKED __attribute__((packed))
  55 #else
  56 #define EPOLL_PACKED
  57 #endif
  58
  59 struct epoll_event {
  60         __u32 events;
  61         __u64 data;
  62 } EPOLL_PACKED;
  63
  64 #ifdef __KERNEL__
  65
  66 /* Forward declarations to avoid compiler errors */
  67 struct file;
  68
  69
  70 #ifdef CONFIG_EPOLL
  71
  72 /* Used to initialize the epoll bits inside the "struct file" */
  73 static inline void eventpoll_init_file(struct file *file)
  74 {
  75         INIT_LIST_HEAD(&file->f_ep_links);
  76         INIT_LIST_HEAD(&file->f_tfile_llink);
  77 }
  78
  79
  80 /* Used to release the epoll bits inside the "struct file" */
  81 void eventpoll_release_file(struct file *file);
  82
  83 /*
  84  * This is called from inside fs/file_table.c:__fput() to unlink files
  85  * from the eventpoll interface. We need to have this facility to cleanup
  86  * correctly files that are closed without being removed from the eventpoll
  87  * interface.
  88  */
  89 static inline void eventpoll_release(struct file *file)
  90 {
  91
  92         /*
  93          * Fast check to avoid the get/release of the semaphore. Since
  94          * we're doing this outside the semaphore lock, it might return
  95          * false negatives, but we don't care. It'll help in 99.99% of cases
  96          * to avoid the semaphore lock. False positives simply cannot happen
  97          * because the file in on the way to be removed and nobody ( but
  98          * eventpoll ) has still a reference to this file.
  99          */
 100         if (likely(list_empty(&file->f_ep_links)))
 101                 return;
 102
 103         /*
 104          * The file is being closed while it is still linked to an epoll
 105          * descriptor. We need to handle this by correctly unlinking it
 106          * from its containers.
 107          */
 108         eventpoll_release_file(file);
 109 }
 110
 111 #else
 112
 113 static inline void eventpoll_init_file(struct file *file) {}
 114 static inline void eventpoll_release(struct file *file) {}
 115
 116 #endif
 117
 118 #endif /* #ifdef __KERNEL__ */
 119
 120 #endif /* #ifndef _LINUX_EVENTPOLL_H */
 121